Treatment of copper ores



Patented Sept. 23, 1924.

UNITED STATES WALTER GEORGE PERKINS, OF LONDON,

mars, 'ro METALS rnonuc'rron comr OF NEW YORK, N. Y.

ENGLAND, nssrenon, BY nnsnn nssren- ANY or nonrn AMERICA mconromrnn,

TREATMENT OF COPPER ORES.

R0 Drawing.

To all whom it may concern:

Be it known that I, WALTER Gnonen PER- KINS, a subject of the King ofEngland, residing in London, England, have invented certain new anduseful Improvements in the Treatment of Copper Ores, of which 'thefollowing is a specification.

This invention consists of improvements in or relating to the treatmentof copper ores.

In the s ecification of United States application erial No. 494,381 isdescribed a process for the treatment of ores containing oxidized coppercompounds, for the recovery of the contained metal therefrom byhydrometallurgical methods. The pres ent invention relates to adevelopment from that process and deals with the treatment of ores whichcontain one or more nonoxidized compounds including sulphide of copper,with or without arsenides and antimonides of copper, or phosphorouscompounds of copper.

There are many ores of copper, of which the porphyries are an example,which contain not only oxidized compounds, such as oxide, silicate orcarbonate of copper, but also contain copper sulphide and othernonoxidized compounds of copper, and one object of this invention is toextract the copper effectively from such ores.

According to this invention a process for the treatment of an orecontaining one or more non-oxidized compounds of copper includingsulphide of copper comprises roasting the crushed ore with access of airat such a temperature that copper sulphide is converted into coppersulphate with a corresponding swelling, then heating the oxidizedmaterial in the presence of a reducing gas, for such a short time and atsuch a low temperature as to reduce the copper compounds without meltingor alloying the copper and without fritting the gangue and so that thereduced material is obtained in a porous condition, and there aftersubmitting the product to a leaching operation with an anmoniacalsolvent of co per in the presence of air or oxygen.

I have found that if, during roasting, the temperature is carried highenough to con- Vert the copper sulphide directly into cop- Applicatlonfiled August 7, 1922. Serial No. 580,298.

per oxide, if, for example, temperatures of 700 C. and upward areemployed, the solubillty of the copper material produced in thesubsequent reduction is seriously im- At the same time I prefer to roastto such a an extent that any iron sulphate produced from iron sulphidein the ore is converted as far as possible into iron oxide. Thisre-action is completed at about 530 C.

For this purpose the preferred range of temperature is between 350 C.and 600 C. but a temperature as high as 700 C. can be used withoutentirely sacrificing the ad vantage of the process.

It is preferred that the roasted ore be heated in the reducing gas to atemperature between 300 C. and 400 C. so as to reduce the copper to aporous soluble form and to. eliminate a large proportion of the sulphurfrom the copper sulphate in the form of sulphur dioxide and sulphurtrioxide.

The preferred ammoniacal liquor for dissolving the copper is one thatcontains for one part of NH not less than 0.8 part of G0,; the presenceof CO, is not so necessary for the solution of any remaining sulphate ofcopper, or basic sulphate of copper.

In carrying the invention into practice the ore is crushed to thenecessary mesh to ensure complete decomposition of the minerals in thesubsequent treatment. The crushed ore is then roasted, say for l to 3hours, at a temperature between 350 C. and 500 C. to convert thesulphides of copper and iron to copper sulphate and iron sulphate.During this stage a considerable swelling occurs, which is a desirablefeature. The temperature is then raised, say to 600 C. for such a time(1 to 2 hours) as to convert the sulphate of iron into oxide of ironwithout decomposing the copper sulphate.

Whatever the composition of the ore was to start with, the copper is nowentirely in the oxidized state.

The roasted 'ore, while still hot, is then passed into or through anatmos here of reducing gas. It is found that if t e roasted ore bereduced at a temperature much exceedin 400 C. (say at a temperature of500 or higher), the reduced copper material is more sparingly soluble inthe ammoniacal li uor, and again as the heating of the materia iscontinued the solubility of the copper diminishes.

It is preferred that reduction be earned out between 300 C. and 400 C.so as to reduce the copper to a porous soluble form and to eliminate alarge pro ortion of the sulphur from the copper su phate 1n the form'ofS0 and S0,. The reduction takes lace very rapidly and is usuallycomplete in about 15 to 20 minutes for articles below one-twentieth ofan inch in iameter. The particles of reduced copper material mom acharacteristic porous conditlon, readily permeable to liquids. Aparticle adheres to the tongue and a drop of water when placed on it isabsorbed instantly. After coohng, the ore is subjected to a leachingoperation in an ammomacal solution of cop r with access of air, andsubstantially a of the copper is separated out from the solution byboiling o the ammonia.

The process of reducing the oxidized copper compounds, leaching with asolvent of copper, and separating the copper from the solution may allbe carried out as described in detail in the s cification of UnitedStates application Serial No. 494,381.

Where the dissolved ammonium salt of copper is combined with someradicle other than 00,, such for example as a S0,, radicle, the copperexists therein as a compound of ammonia, copper and that radicle; forexample, copper sulphate will be present as ammonium copper sulphate.When the solution is boiled for the recovery of both copper and ofammonia, only the copper present as ammonium copper carbonate isprecipitated, mainly as copper oxide. On the other hand the copperexisting in solution as ammonium copper sulphate is not preci itatedhowever long its solution may boiled; to effect recipitation of thecopper in this case, and the recovery of its associated ammonia, theequivalent of a caustic or carbonated alkali must be added, eitherbefore or during the expulsion of the ammonia when the copper is throwndown as oxide or carbonate. The equivalent of any alkali can be usedwhich produces a soluble sulphate as'the result of such reaction: limecannot be so effectively used since some cal cium sulphate would beprecipitated with the copper oxide, etc. Magnesium oxide may be usedafter the distillation of ammonia or at the later stages of thedistillation.

The following is an actual example of the application of this inventionThe ore was a mill roduct from the Otavi Mine, South Africa, andcontained 3.80% copper, 2.35% being in the oxidized form, and 1.405% inthe sulphide form.

This material was roasted in a mufie furnace, with free access of air,for :-1% hours at 400 C, 2 additional hours at 500 C 1 additional hoursat 525 C.

The roasted product was reduced in coal gas at a temperature of 325350C. for about half-an-hour, and the resulting product was ultimatelyleached with cupric ammonium carbonate solution, with a result that thetailings assayed 0.36% Cu. the recovery of copper in solution being86.8%.

What I claim as mly invention and desire to secure by Letters atentis 1. A process for the treatment of an ore containing sulphide or coper which comprises roasting the crushe ore with access of air at such atemperature that co per sulphide is converted into copper sulp ate witha corresponding swelling, then heating the oxidized material in thepresence of a reducin gas for such a short time and at such a owtemperature as to reduce copper compounds without melting the copper andwithout frit-ting the gangue and so that the reduced material isobtained in a porous condition, and thereafter submitting the product toa leaching operation with an ammoniacal solvent of copper in thepresence of oxygen.

2. process for the treatment of an ore containing1 sulphide of coppercomprising roasting t e crushed ore with access of air so that coppersulphide is converted to copper sulphate and an iron sul hate isconverted into iron oxi e but wit out converting copper sulphate tocopper oxide, heating the oxidized material in the presence of areducing gas for such a short time and at such a low temperature as toreduce copper compounds without melting the cop r and without frittingthe gangue and so t at the reduced material is obtained in a porouscondition, and thereafter submitting the product to a leaching operationwith an ammoniacal solvent of copper in the presence of oxygen. a

3. A process for the treatment of an ore containing sulphide of co perwhich comprises roasting the crushe ore with access of air at atemperature between 350 C. and 700 C. then heating the oxidized materialin the presence of a reducing gas for such a short time and at such alow temperature as to reduce copper compounds without melting the copperand without frittin the gangue' and so that the reduced materi v isobtained in a porous condition, and thereafter submitting the product toa leaching operation with an ammoniacal solvent of copper in thepresence of oxygen.

4. A process for the treatment of an ore containln both oxidized andnon-oxidized compoun s of copper including sulphide of copper whichcomprises roasting the crushed ore with access of air at such atemperature that copper sulphide is converted into copper sulp ate witha corresponding swelling, then heating the oxidized material in thepresence of a reducing gas for such a short time and at such a lowtemperature as to reduce copper compounds without melting the copper andwithout fritting the gangue and so that the reduced material is obtainedin a porous condition, and thereafter submitting the product to aleaching operation with an ammoniacal solvent of copper in the presenceof oxygen.

5. A process for the treatment of an ore containing sulphide of copperwhich comprises effecting an oxidizing roast of the crushed ore at atemperature between 350 C. and 700 C. then heating the oxidized materialin a reducing gas at-a temperature between 300 C. and 400 C. so as toreduce the copper to a porous soluble form and leaching the product witha solvent of copper in the presence of oxygen.

6. A process for the treatment of an ore containin sulphide of cop erand iron compounds w ich comprises e ecting an oxidizing roast of thecrushed ore atatemperature between 350 0., and 500 0., thereaftereffecting an oxidizing roast at a higher temperature to convert the ironcompounds into oxide, then heating in a reducing gas at a temperaturebetween 300 C. and 400 C. so as to reduce the copper to a porous solubleform, and leaching the product with a solvent of copper in the presenceof oxygen.

A process for the treatment of an ore containm sulphide of cop er andiron compounds w ich comprises e ecting an oxidizing roast of thecrushed ore at a temperature between 350 C. and 500 C., thereaftereffecting an oxidizing roast at a higher temperature to convert theiror. compounds into oxide, then heating in a reducing gas at atemperature between 300 C. and 400 C. so as to reduce the copper to aporous soluble form, and leaching the product with an ammoniacal solventof copper in the presence of air.

8. A process for the treatment of ores containing sulphide of copperwhich comprises efi'ecting an oxidizing roast of the crushed ore at sucha temperature as to convert the copper sulphide to sulphate, thereafterheating in a reducing gas so asto reduce copper compounds withoutmelting the copper or fritting the gangue leaching the product with anammoniacal solvent of copper in the presence of oxygen, and sub ectingthe solution to distillation to eliminate ammonia with the addition ofan alkali of the kind described.

In testimony whereof I have signed my name to this'specification in thepresence of two subscribing witnesses.

WALTER GEORGE PERKINS.

Witnesses:

Tnos. J. TAPLIN, Jr.,

H. C HAWKINS.

